In recent years, 3rd generation mobile communication systems (3G) including a W-CDMA (Wideband-Code Division Multiple Access) scheme have been supplied worldwide. Additionally, next-generation mobile communication systems for implementing new high-speed communication are being studied. As the next-generation mobile communication systems, 4th generation mobile communication systems (4G) having a downstream communication rate of 100 Mbps to 1 Gbps are being studied.
However, 3G and 4G have a large difference in terms of the system configuration. To bridge the technical and temporal gap between 3G and 4G and implement a smooth transition to 4G, E-UTRA (Evolved Universal Terrestrial Radio Access), which implements a downstream communication rate of about 100 Mbps by employing the same frequency as in 3G and introducing a new technique as a candidate for 4G, is being actively discussed by 3GPP (3rd Generation Partnership Project).
In E-UTRA, which is the next-generation mobile communication system, an OFDMA (Orthogonal Frequency Division Multiple Access) scheme is adopted as that of the downlink. In E-UTRA, a technique called AMC (Adaptive Modulation and Coding), which adaptively changes a plurality of modulation schemes (modulation rates) or coding rates, is being adopted. Also, in E-UTRA, a MIMO (Multiple Input Multiple Output) transmission mode is adopted in which a plurality of antennas is provided at both sides of a transmission side and a reception side and data is transmitted/received using the plurality of antennas.
For the MIMO transmission mode, transmission modes such as spatial multiplexing (SM), beam forming (BF), and spatial diversity (single-stream transmit diversity mode) (SD) have been considered, and the switching for the three transmission modes has been proposed (Non-Patent Citation 1).    [Non-Patent Citation 1] 3GPP R1-060774 “Evaluation of Downlink MIMO Transmission Mode Selection”    [Non-Patent Citation 2] 3GPP TSG-Ran Working Group 1 Meeting #44, R1-060647, DL Adaptive STTD/SM Performance Evaluation for E-UTRA.